Variable power riflescope with tilting reticle and erector tube



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Dec. 15, 1964 D. J. BURRIS ETAL 3,161,716 VARIABLE POWER RIFLESCOPE WITHTILTING RETICLE AND ERECTOR TUBE Filed Feb. 19, 1962 2 Sheets-Sheet 1INVENTORS DONALD J. BUR/PIS JOHN L. MAuLBETscH ,4T ORNEYS 1964 D. J.BURRIS ETAL 3,161,716

VARIABLE POWER RIFLESCOPE WITH TILTING RETICLE AND ERECTOR TUBE FiledFeb. 19, 1962 2 Sheets-Sheet 2 INVENTORS DON/71.0 J. BUR/P/S Joli/34V L,M/IULBETSOH ATTORNEYS United States Patent 3,161,716 VARIABLE POWERRIFLESCOPE WITH TILTING RETICLE AND ERECTOR TUBE Donald J. Burris,Broomfield, Colo., and John L. Maulbetsch, Northampton, Mass., assignorsto Redfield Gun Sight Company, Denver, Colo., a limited partnership ofColorado Filed Feb. 19, 1962, Ser. No. 173,922 8 Claims. (Cl. 88--32)This invention relates to optical sighting devices and, moreparticularly, to improvements in telescopic rifle sights of theinternally adjustable type that include a reticle.

This application is a continuation in part of our application forLetters Patent of the United States Serial Number 100,100 filed April 3,1961, now abandoned.

A number of significant advances in the design and construction ofinternally adjustable rifiescopes have been made in recent years whichhave contributed materially to their versatility, ruggedness,dependability and accuracy. Among the most important of these have beenthe feature by which the reticle appears to always remain centered inthe field of view irrespective of the adjustments made in the scope tointroduce corrections in the line of sight to compensate for windage,the distance to the target, the ballistic characteristics of aparticular cartridge and, primarily, to 2ero-in the scope to the axis ofthe gun barrel because, due to the dimensional variations in the mounts,the mechanical axis of the scope is rarely exactly in line with the gunbarrel. The fact that the trajectory of a bullet does not coincide withthe line of sight which is always straight necessitates thesecorrections.

A riflescope includes a reticle which provides some means for definingan aiming point supposedly coincident with the point of impact of thebullet on the target. Reticles take many forms, the most common of whichare the cross-hair, dot and post types and these patterns may takeeither the form of filaments or other materials mounted in a frame or adesign engraved, etched or otherwise deposited on a piece of glass.There are certain rather standard design requirements insofar as reticleplacement within the optical system are concerned that must be followedand many of the refinements in scope design, such as the centeredreticle feature, should take these standard requirements into account.For instance, there are usually two image planes within a riflescope inwhich a sharp image of the target is produced. One lies at or near thefocal plane of the objective lens system which is near the front of thescope (at or near depending on whether the objectives are set forviewing at infinity or at a nearer target, 100 yards, for instance, thelatter being the usual case), and the other is at or near the focalplane of the lens system consisting of objective lenses and erector lenssystem. This second image plane is the one usually viewed by theobserver through the eyepiece and is, therefore, adjacent to theshooters eye and may be referred to as an eyepiece image plane. Thefirst one may be referred to as objective image plane. If the image ofthe reticle, as viewed by the shooter is to be superimposed upon theviewed image of the target in a sharp and well defined manner withoutshowing any parallax, then the reticle must be located either in thefirst image plane or in the second image plane. Actually, neither ofthese planes is accurately fixed as they vary with the distance to thetarget being sighted; however, from a practical standpoint, they aresubstantially fixed, as most targets that require the use of a scope inthe first place are far enough away that variations in distancesintroduce only a minute displacement of these image planes and thereforeonly a slight amount of parallax between target image and reticle imagewill result.

A well designed scope must also include a diaphragm that limits thefield of view as seen through the optical system and is known as a fieldstop. The purpose of this diaphragm is to give a sharply delineatedboundary to the field, and further, it serves to prevent unwantedinternal reflections. If a diaphragm is not used the field is limited byvarious apertures in the optical system which are not in sharp focus tothe shooter producing a fading out of the field which is a mostundesirable eifect.

This diaphragm should also be located in one of the two image planes ofthe scope it a sharp and well-defined field is to be maintained. It maybe in the same image plane as the one where the reticle is placed or thereticle may be placed in one image plane and the diaphragm in the other.For practical reasons and also because of optical considerations, thisdiaphragm may be slightly displaced longitudinally relative to thecenter of the image plane. The reticle is focused mainly for the centralregion of the field while the diaphragm acts on the edges of the field.

Bearing in mind the foregoing relationships, the optical system in ariflescope should, in addition, provide means for maintaining the aimingpoint of the reticle centered in the field of view defined by thediaphragm throughout the maximum adjustment range of the system tocompensate for windage and elevation. This refinement presents a muchmore difficult problem. One possible solution is to mount the reticlewithin the main scope barrel at the eyepiece image plane to maintainsame in sharp focus as aforementioned, and mount the tube of otheradjustable support for the erector lens system for limited universalmovement relative to the barrel about a center that also falls withinthe eyepiece image plane. From the practical standpoint, it becomesextremely difficult, if not impossible, mechanically to locate andmaintain the center of universal movement of the erec tor lens systemsupport coincident with the aiming point defined by the reticle or, forthat matter, even in the same plane; however, this is not an overridingconsideration as the off-center relationship that results when thecenter of universal movement of the erector lens tube is displaced asmall fraction of an inch from the image plane containing the reticle,while noticeable, is not too disturbing to the viewer. Any greaterseparation between the center of universal movement of the erector lenssystem and adjustable support therefor from the image plane in which thereticle is located does, however, materially affect the centering of thereticle assuming that the diaphragm is mounted for movement with theerector lens system. In other words, when the center of universalmovement of the erector lens system and mount therefor are displaced anyappreciable distance from the reticle and the latter is located in theeyepiece image plane, some relative movement between the diaphragmcarried in the erector lens tube and the reticle which 0ccupies a fixedposition within the barrel must take place when angular adjustments ofthe erector lens system are made to introduce windage and elevationcorrections; thus, the reticle will not remain centered within the fieldof view defined by the diaphragm.

A better solution to the centered reticle problem is to mount thereticle in the same adjustable support that carries the erector lenssystem and the diaphragm thus eliminating any relative movementtherebetween due to the fact that a fixed relationship exists among allelements that cooperate to establish the line of sight and, even thoughthey are adjustable by reason of their common adjustable support, all ofthem move in fixed ratio to one another thus maintaining true centeringof the aiming point within the field of view. The US. patent toKolhnorgen et a1. 2,955,512 which is now owned by the assignee of thisapplication, recognized this important relationship; however, at thetime it was felt that the center of universal movement of the erectorlens system should be located approximately in the eyepiece image planemuch in the same manner as in the centered reticle system previouslydiscussed in which the reticle was separately and fixedly mounted in themain barrel, if true centering was to be achieved. It has now been foundin accordance with the teaching of the instant application that thelocation of the center of universal movement of the erector lens systemin relation to the eyepiece image plane is not particularly significantinsofar as the centered reticle feature is concerned as long as both thediaphragm and reticle are mounted on the optical axis of the erectorlens system for movement therewith. From a different standpoint,however, it is still highly desirable to locate the center of universalmovement of the erector lens system adjacent one end of the erector lenstube and the means for adjusting same to correct for windage andelevation at the other end as, by so doing, utilization is made of along lever arm having the advantage of extremely fine windage andelevation adjustments and, more important, the field of view through thescope will remain more or less centered in the eyepiece lenses. In otherwords, the more closely the center of movement of the erector lensassembly and the adjustment mechanism therefor approach one another, thecoarser the adjustment becomes because, with a short lever arm a greaterangular shift takes place in the optical axis of the erector lens systemrelative to the fixed optical axis defined by the centers of objectiveand ocular lens systems. The net result of this is that the center ofuniversal movement of the erector lens system is, in fact, preferablylocated in close proximity to the eyepiece image plane but for thepurposes of maintaining the field of view centered in the eyepiecelenses and to realize fine windage and elevation adjustments rather thanto preserve the centered reticle feature which is more or lessindependent of the location of this center of universal movement whenboth the diaphragm and reticle are carried by the same mount as theerector lenses.

Now, the Kollmorgen et al. reticle-centering system previously describedwherein the reticle is carried by the erector lens tube and located inthe objective image plane along with the other system where the reticleis mounted in fixed position in the main barrel and located in theeyepiece image plane, have both proven reasonably satisfactory for usein fixed-power riflescopes; however, neither one will perform well in avariable-power scope as each introduces new problems even though thereticle remains farily Well centered. For example, if the optical systemof the Kollmorgen et a1. Patent 2,955,512 were adopted for use in avariable-power scope, the reticle would be magnified in directproportion to the degree of magnification of the image whenever thelatter was varied due to the location of the reticle essentially in theobjective image plane. This apparent change in size of the reticle uponvarying the degree of magnification of the image is disturbing to theuser and, more important, makes it difficult to accurately locate theaiming point on the target due to the relative enlargement of theintersection of the cross-hairs, post-tip or dot. If, on the other hand,the reticle size remained constant and that at which it would appear atthe minimum power, an increase in magnification of the target imagewould result in the sighting point obscuring a smaller area of thetarget and permit extremely accurate location of the point of impact.This desirable end can be attained without disturbing the centeredreticle feature in accordance with the teaching of the instant inventionby relocating the reticle in the rear extremity of the erector lens tubeand in the eyepiece image plane. For best results, the diaphragm shouldremain, as in the Kollmorgen construction, located in this eyepieceimage plane so that the size of the field of view will, likewise, remainconstant and in sharp focus through the entire range of target imagemagnification.

The construction wherein the reticle is fixedly mounted in the mainscope barrel at the eyepiece image plane is subject to a much moreserious deficiency in variablepower scopes even though there is noapparent increase or decrease in reticle size accompanying changes inthe degree of target image magnification. Unless the sighting pointdefined by the reticle is positioned exactly on the optical axis of theerector lens system, the point of impact of the bullet will appear tomove in relation to the target as the power of the scope is changed.When this happens, the accuracy of the rifiescope as a sighting deviceis lost. In other words, the aiming point will no longer coincide withthe point of impact nor can this discrepancy be compensated for byintroducing appropriate windage and elevation corrections as the errorwill still be present at other degrees of magnification. This is not afactor in fixed-power scopes because, once the scope is assembled, thecenter of the reticle and the axis of the erector lens system occupy afixed relationship to one another and to the trajectory of the bulletwhich does not change. Any displacement of the reticle off the opticalaxis of the erector lens system remains constant and will, therefore, becompensated for by the windage and elevation corrections even though theactual adjustments made are not all caused by wind conditions and thedrop of the bullet but include increments to correct for misalignment ofthe reticle with the optical axis.

No such simple solution is available in a variable-power scope whereinthe reticle is mounted in the eyepiece image plane because, for trueaccuracy, the aiming point must be exactly on the optical axis of theerector lens system or, any error present, will show up immediately asthe image size is varied relative to the reticle size in the form of ashift in the point of impact. Now, it is a practical impossibility tokeep the aiming point of a reticle fixedly mounted within the main scopebarrel always on the optical axis of the erector lens system which ismoveable in order to introduce windage and elevation corrections.Theoretically, of course, the aiming point of a reticle mounted in themain barrel could be placed exactly on the optical axis of the erectorlens system and the latter be mounted for limited universal movementabout the aiming point to produce the desired result; however,mechanically, this theoretical condition cannot be achieved with anysystem that would be practical for use in a riflescope.

It is possible, however, to mount the reticle on the erector lens tubeand also provide means for relocating the aiming point of the latterexactly on the optical axis of the erector lens system thus achievingtrue accuracy in a variable-power riflescope while, incidentally,retaining the centered reticle feature, maintaining both the reticle andfield of view defined by the diaphragm or field stop a constant sizethroughout the entire range of variation in image magnification, andaccomplish these desirable ends substantially independent of the centerof universal movement of the erector lens system. It is the foregoingthat comprises the most significant contribution of the presentinvention.

Accordingly, it is the principal object of the present invention toprovide a novel and improved internally adjustable riflescope of thetype having a reticle incorporated therein capable of defining an aimingpoint and point of impact with great accuracy.

A second object is the provision of an internally adjustable riflescopewherein the reticle always remains apparently centered within the fieldof view and in focus irrespective of the windage and elevationcorrections introduced in the optical axis of the erector lens system orthe location of the center of universal movement of the latter relativeto the image plane in which said reticle is positioned.

Another objective is to provide an optical system especially suited foruse in a variable-power internally adjustable riflescope that maintainsthe reticle image a constant size despite variations in the degree ofmagnification of the target image.

Still another object is the provision of an adjustable reticle assemblythat enables the aiming point of the reticle to be located precisely onthe optical axis of the erector lens system.

An additional object of the invention is to provide an improved andsimplified universal mounting for the erector lens system in aninternally adjustable riflescope.

Further objects of the invention herein described are the provisions ofa telescopic sighting device for rifles and the like which is rugged,versatile, easy to operate, compact, accurate, relatively free ofservice problems, lightweight and decorative in appearance.

Other objects will be in part apparent and in part pointed outspecifically hereinafter in connection with the description thatfollows, and in which:

FIGURE 1 is a vertical diametrical section showing the internallyadjustable riflescope of the present invention;

FIGURE 2 is a fragmentary diametrical section to an enlarged scale,portions of which have been broken away to conserve space, showing thedetails of the erector lens assembly and associated adjustmentstructure;

FIGURE 3 is a transverse section taken along line 33 of FIGURE 2illustrating the externally-located ring which is rotated to vary thespacing and longitudinal position of the erector lenses thus alteringthe degree of image magnification;

FIGURE 4 is a transverse section taken along line 44 of FIGURE 2 showingthe windage and elevation adjustment controls and their operativeconnection with the erector lens assembly;

FIGURE 5 is a top plan view of the erector lens tube and the meansoperatively associated therewith for changing the position of theerector lenses to change the power of the scope;

FIGURE 6 is a development of the rotating cam tube and cam slots thereinwhich envelops the erector lens tube and turns relative thereto to alterthe position of the erector lenses;

FIGURE 7 is a rear elevation of a cross-hair-type reticle assemblyshowing the means for centering same;

FIGURE 8 is a diametrical section through the reticle assembly of FIGURE7; and,

FIGURE 9 is a fragmentary diametrical section to an enlarged scaleillustrating a modified ball and socket type pivotal connection betweenthe erector lens tube and barrel that may be substituted for the elasticcoupling of FIGURES l and 2.

Referring now to the drawings for a detailed description of the presentinvention and, in particular, to FIGURES 1 and 2 for this purpose, theriflescope will be seen to include basically a tubular barrel 10 havingan objective lens assembly 12 mounted on its remote end, an eyepiece orocular lens assembly 14 mounted on the near end of the barrel, and anerector lens assembly mounted inside the barrel, the latter having beendesignated in a general way by reference numeral 16. The invention thatforms the subject matter hereof has been illustrated and will bediscussed in detail as it relates to a riflescope although it is by nomeans restricted to this specific application and the principles thereofwould be equally useful in other optical sighting instruments. In fact,the particular riflescope shown is of the variable-power type ascontrasted with those employing fixed magnification as it is the formerscope in which many of the features to be set forth herein find theirgreatest utility although all of them, with the possible exception ofthe features relating specifically to the means for maintaining a fixedreticle size throughout changes in the degree of image magnification,are also useful in fixed-power sighting devices.

In the particular construction illustrated herein, the objective lensassembly 12 includes a flared barrel extension 18 that threads into themain barrel 10, a lens holder 20 into which the objective lens 22 iscemented or otherwise mounted, and a threaded ring 24 that cooperateswith the barrel extension 18 to hold the lens holder 20 in place. Lens22 may, of course, be of the compound type or the single element typeillustrated depending upon the par ticular optical system employed inthe scope. Functionally, the objective lens assembly reproduces aninverted and reversed image of a real object in a plane normal to theoptical axis defined by the centers of the objective and ocular lenssystems. The location of this plane depends upon the distance to thetarget; however, for practical purposes the target viewed through ariflescope can be considered an infinite distance away meaning that thelight reflected therefrom enters the scope in the form of parallel rayswhich place the image plane at the focal length of the lens where itstays. In the present optical system, objective lens image plane wouldbe located a slight distance ahead of collector lens 26 mounted in thefront end of erector lens tube 28 as represented by plane AA. Thecollector lens merely functions to concentrate the rays from theobjective lens system and direct them into the erectors. The unit willfunction quite well without the collector lens, however, and it has beenincluded merely to illustrate the preferred optical arrangement.

At the other or rear extremity of the barrel 10 is the eyepiece orocular lens assembly 14 which in several respects is quite similar tothe objective lens assembly just described. For instance, it alsoincludes an internallythreaded barrel extension 30 which has a flaredportion 32 interconnecting small diameter and large diameter tubularsections that have been designated by numerals 34 and 36, respectively.The small tubular section 34 threads onto the externally-threaded end ofthe main barrel 10 enabling the optical system to be adjusted tocooperate with the users eye which forms a part thereof. Lock ring 38locks the barrel extension 30 in adjusted position. As shown, the largertubular section 36 is internally-threaded and provides a shoulder 40against which compound lens 42 rests and is secured in place byretaining ring 44. The remaining lens element 46 is mounted within aring 48 that threads into the rear extremity of tubular section 36. Hereagain, the particular construction and arrangement of lens elements andmounts therefor can be varied to suit particular requirements and theones shown herein are intended as being merely illustrative of oneocular lens assembly that will function to focus upon the erected imagereproduced by the erector lens assembly in the erector lens image planedesignated B-B in FIGURES l and 2. It should be mentioned that theobjective and erector lens assemblies cooperate with one another tolocate the second image plane B-B which remains fixed for all practicalpurposes assuming the optical system is focused upon a target located aconsiderable distance from the scope. Adjustment of the eyepiece orocular lens system merely brings the erect image in the erector lensimage plane B-B into sharp focus and the precise location of said ocularlens will, therefore, vary with the requirements of the viewers eye.

The erector lens assembly 16, in a fixed-power riflescope, has one primefunction, namely, the reinversion and reversal of the inverted andreversed target image reproduced by the objective lens system althoughin some scopes it may also be used to accomplish angular adjustment ofthe line of sight relative to the optical axis defined by the centers ofthe objective and eyepiece lens systems to compensate for errorsinherent in the trajectory of the bullet. In a variable-power riflescopesuch as that illustrated herein, a third function is added to thosealready mentioned and this is to increase or decrease the degree oftarget image magnification. In a fixed-power scope the foregoingfunctions are accomplished by at least one and preferably two erectorlens elements 50 and 52 mounted within an erector lens tube 28 inposition to produce a.

focused erect image of the target in a focal plane BB located, in mostinstances, adjacent the rear end of the barrel 10. The erector lens tube28 is housed within the barrel and is of a lesser diameter than thelatter so as to permit limited movement relative thereto about a pointof more-or-less universal movement defined by a coupling 54 located inspaced longitudinal relation to the windage and elevation adjustmentmechanisms that have been designated in a general Way by referencenumeral 56 and which also interconnect the barrel and erector lens tube.

In a variable-power scope on the other hand, these same elements arerequired although at least two erector lens elements 50 and 52 arenecessary and provision must be made for adjusting their longitudinalpositions relative to one another and with respect to the ocular andobjective lens systems for purposes of accomplishing variation in targetimage magnification, Even though these erector lenses move back andforth along the erector lens tube, the erect focused target imageproduced thereby must remain substantially fixed in focal plane BB.

In the specific embodiment illustrated herein, a ring 58 containing arearwardly-facing shoulder 60 is mounted within the rear extremity ofthe main lens barrel 10 and retained non-rotatably in place with setscrews 62. The rear end of the erector lens tube 28 is provided with aninternally-threaded enlargement 64 that defines a shoulder 66 spacedrearwardly of shoulder 60 and in opposed relation thereto. Between theseshoulders 60 and 66 and the radially-spaced opposed wall surfaces of thering 58 and erector lens tube 28 is placed an elastic coupling 54 thatis preferably bonded to these surfaces in accordance with the teachingof US. Patent 2,948,188 that is owned in common with the instantapplication. This bonded and preferably vulcanized coupling 54 perm-itslimited universal movement of the erector lens tube and associatedelements relative to the main barrel and thus provides the means bywhich corrections for elevation and windage may be introduced into theoptical system.

The specific mechanism 56 by which the line of sight is adjustedrelative to the optical axis can best be seen in FIGURES 1, 2 and 4 towhich reference will now be made. The interior surface of the mainbarrel 10 is provided with a longi-tudinally-extending groove 68 withinwhich is retained a bowed leaf spring 70. The intermediate portion ofthis spring bears against the erector lens tube 28 at a point spacedlongitudinally from its center of limited universal movement and biasesthe latter toward a diametrically opposed point on the inside surface ofthe main barrel.

Angularly spaced approximately 135 on opposite sides of spring 70 arethe .points of contact of windage and elevation control screws 72 and74, respectively, that are carried by the main barrel for movementagainst the erector lens tube in opposition to the bias exerted thereonby said spring. When the scope is mounted on a rifle barrel, it occupiesthe position shown in FIGURE 4 wherein the axis of the windage controlscrew 72 is substantially horizontal, that of the elevation controlscrew is substantially vertical and the spring 70 is equiangularlyspaced therebetween to urge the erector lens tube against both controlssimultaneously irrespective of their adjusted positions. Obviously, withthe axes of these two adjustment screws disposed at 90 to one another,using one screw to shift the line of sight in one plane does not shiftthe line of sight in a plane normal thereto due to the broad flat endson the screws and the limited angular adjustment provided within theconfines of the barrel.

The mount for these screws comprises a saddle-forming element 76 whichis secured to the exterior surface of the barrel by internally andexternally threaded flanged tubular members 78 that also screw into thebarrel wall. Each of the latter members has a radial flange 80 borderingthe outer extremity thereof and an externally-threaded outstanding rimencircling the flange 82 to define a recess 84 adapted to receive theslotted head 86 of the adjustment screw 72 or 74. A protective cap 88 isdetachably mounted upon the externally threaded rim 82 to preventmoisture, dust and other foreign matter from entering the assembly 56and possibly the optical system. The abovedescribed windage andelevation controls can assume any one of several different forms andthose shown are intended as merely being illustrative of one type thatis simple, accurate and able to withstand considerable recoil withoutbecoming damaged or moving out of adjustment.

Again with reference to FIGURES 1 and 2, it will be seen that thereticle 90 along with the diaphragm 92 are both located in the eyepieceimage plane BB and, in addition, are carried by the erector lens tubefor movement therewith; yet, the center of universal movement of theerector lens assembly 16 as defined by resilient coupling 54 is not inthis same plane. In fact, the center of universal movement defined bycoupling 54 may be located anywhere along the erector lens tube as longas it is spaced longitudinally from the elevation and windage adjustmentmechanism 56 to provide a lever arm about which the line of sight canshift relative to the optical axis in order to preserve the centeredreticle feature; however, it is preferably located in close proximity tothe eyepiece image plane, as aforementioned, to keep the field of viewmore or less centered in the eyepiece. As long as the diaphragm 92 andreticle 90 are both moveable with the erector lens assembly, the reticlewill remain centered in the field of view defined by the aperture in thediaphragm. In addition, as is the case here, the reticle and diaphragmwill remain in focus because they are located in eyepiece image planeBB. In a fixedpower scope, as aforementioned, either the reticle or thediaphragm or both may also be located in the objective image plane AAand remain centered and in sharp focus. A variable-power scope such asthat illustrated herein, however, necessitates placement of both thereticle and diaphragm in the eyepiece image plane BB if the apparentsize thereof is to remain constant throughout the entire range of changein the degree of image magnification. This alone is not enough as thesighting point 94 of the reticle 90 must also be located precisely onthe optical axis of the erector lens system in order to avoid a shift inthe point of impact when the degree of magnification is decreased orincreased as has already been explained in considerable detail. 1

Reference will now be made to FIGURES 1, 2, 7 and 8 for a detaileddescription of the mechanism by which the aforementioned desirable endshave been realized in the riflescope forming the subject matter of theinstant inven- .tion. An internally and externally threaded ring 96having an annular interrupted stop-forming flange 98 on the forward endthereof is threaded into the internally threaded enlargement 64 on therear extremity of the erector lens tube. The diaphragm 92 comprises aring having a frusto-conical inner surface 100 terminating at itsforward extremity in a circular edge 102 that defines an aperturerestricting the field of view through the optical system to an area lessthan that encompassed by other elements of the optical system.Preferably, the aperture defined by edge 102 is such that the maximumdeviation in the erector lens tube relative to the main barrel will notbe sufiicient to allow the lens holder 20 for the objective lens 22 toappear in the field of view. The exterior surface 104 of diaphragm 92is, in the form shown, smooth and generally cylindrical. Most important,however, is the fact that the outside diameter of this diaphragm-formingring 92 is somewhat less than the minimum inside diameter of mountingring 96 as defined by the lands of the internal threads, This allowsring 92 to be shifted radially, i.e. in a plane normal to the opticalaxis of the erector lens system, relative to mounting ring 96. In thatthe diaphragm-forming ring 92 performs the secondary function of themount for the reticle 90, this adjustable feature makes it possible tolocate the sighting point 94 of the cross-hair-type reticle precisely onthe optical axis of the erector lens system thereby eliminating anyshift in the point of impact when the degree of mag nification of thescope is changed. The necessity for such an adjustment arises because ofthe mechanical problems associated with fastening the cross-hairs of thereticle to the diaphragm ring such that their intersection which definesthe sighting point will be exactly at the center of the ring. There are,of course, other possible reasons for misalignment of the sighting pointrelative to the optical axis of the erector lens system which may or maynot be correctable with the structure just described although thisradial reticle adjustment feature is almost always adequate tocompensate for the eccentricity of the sighting point occasioned bymechanical errors in fabricating the reticle.

The diaphragm and associated reticle carried thereby are secured inadjusted position by means of an externallythreaded lock ring 106 thatis screwed into the rear end of mount 96 forcing ring 92 againststop-forming flange 98.

In the assembly of the reticle and diaphragm, they are first looselymounted in the mounting ring 96 and the latter is screwed into the endof the erector lens tube. The sighting point 94 of the reticle is thenrelocated to place same exactly on the optical axis of the erectorlenssystem and any tilt in a cross-hair or post type reticle relative tothe axes of the windage and elevation adjustment screws is eliminated byrotating the diaphragm ring in its mount before tightening the lock ring106.

Next, the means by which the positions of the front and rear erectorlenses 50 and 52 are shifted relative to one another and along theerector lens tube 28 will now be set forth in connection with FIGURES1-6, inclusive. Each of these erector lenses which, in the particularform shown are of the compound double-convex type, are carried inseparate mounts 108 and 110 that are sized to fit inside the erectorlens tube and slide longitudinally therein between collector lens 26 andreticle 90. Each mount has a shoulder 112 against which the lens restsand a retaining ring 114 that fits over the end of the mount holding thelens in place against the shoulder. The erector lens tube is providedwith a longitudinal slot 116 adapted to receive a pair of slide blocks118 and 120 for slideable movement in the direction of the lengththereof. These slide blocks 118 and 120 are secured, respectively, tomounts 108 and 110 by screws 122 and 124 which each have headsprojecting outwardly beyond the surface of the erector lens tube inposition to be received within cam slots 126 and 128 provided in thewalls of rotatable cam tube 130.

Cam tube 130 encircles the erector lens tube 28 between the points ofcontact of the windage and elevation adjustment screws 72 and 74therewith and ring 58. This tube 130 is mounted for rotation relative tothe erector lens tube which, as previously noted, is nonrotatablyattached to the main scope barrel 10. Rotation of cam tube 130 isaccomplished by means of externally-located adjusting ring 132 thatencircles the barrel immediately ahead of lock ring 38. An annular slot134 in barrel opens onto the exterior surface of the cam tube and theinside surface of the adjusting ring 132, the latter elements beingoperatively interconnected by screw 136 that has the cylindrical portionthereof moving within slot 134 protected by a plug 138. Slot 134, ofcourse, prevents longitudinal movement of the cam tube, screw 136 andadjusting ring 132 relative to the erector lens tube; therefore, uponrotation of the cam tube by means of said external adjusting ring, theheads of screws 122 and 124 moving within cam slots 126 and 128 willcause the erector lens mounts 108 and 110 along with the erector lensescarried thereby to move along the erector lens tube while varying thespacing between one another thus either increasing or decreasing thedegree of magnification of the target image.

The inclination, shape and arrangement of cam slots 126 and 128, as itis most clearly revealed in the develop- 10 ment of cam tube shown inFIGURE 6, are selected such that the focal plane of the system remainsat image plane B--B yet the degree of magnification of the target imagesteadily increases as the positions of these erector lenses is varied.

The inside of adjusting ring 132 is preferably provided with a pair ofannular grooves spaced on opposite sides of screw 136 that are adaptedto receive O-rings 140 These O-rings prevent the metal-to-metal contactand resultant abrasion between the ring and barrel as the former isrotated relative to the latter. Also, they prevent the introduction ofmoisture and other foreign material into the interior of the scope aswell as the escape of the dry nitrogen sometimes introduced and sealedinto the optical system to prevent moisture condensation and theresultant fogging of the lenses. Furthermore, these O-rings absorb anyslight tilt of the adjusting ring relative to the barrel that might betransferred thereto when the erector lens tube is shifted laterally tocorrect for windage and elevation although such deflection is so smallas to be of no consequence especially when, as in the instantconstruction, the mechanism for rotating the cam tube is positionedquite close to the coupling 54.

Finally, with brief reference to FIGURE 9, a modified form of universalcoupling 54m between the erector lens tube 28m and main barrel 10m willbe described. As shown, sleeve 58, has been eliminated and a section ofincreased inside diameter 142 provided at the rear end of the barrel10m. The rear extremity of the erector lens tube 28m has been changed toprovide a spherical outer surface 144 which slides against the enlargedcylindrical section 142 of the main barrel somewhat in the same manneras is found in a ball-and-socket joint. A hollow cylindrical bushing 146is mounted on the spherical wall section 144 of the erector lens tubewith its axis extending substantially radially and normal to saidspherical surface. A spherically-surfaced pivot pin 148 is attachedwithin the enlarged cylindrical section of the barrel in position to fitinside the bushing and form a universal coupling 54m therewith. Such acoupling has certain advantages over the resilient bonded rubbercoupling 54 shown in FIGURES 1 and 2, perhaps the most significant ofwhich is the fact that the center of universal movement defined therebydoes not remain fixed, but rather, shifts around depending upon thedistribution of the compression and tension loads to which it issubjected when adjustments are made, whereas, the ball-and-socketconnection 54m will remain fixed. It might appear that displacing thecenter of universal movement of the erector lens system from a pointsubstantially on the optical axis thereof to one eccentrically locatedon the inside surface of the barrel would cause problems in keeping thereticle in focus, the edge of the field sharp, etc. As a practicalmatter, however, when the coupling 54m is located near one extremity ofthe erector lens tube and the windage and adjustment mechanism at theother, the maximum that the sighting point can move out of the eyepieceimage plane B-B amounts to a very few thousandths of an inch which iswell within the design tolerances of other elements of the system.

Having thus described the several useful and novel features of theriflescope of the present invention, it will be seen that the manyworthwhile objectives for which it was designed have been realized.Although but two different embodiments of the invention have been shownin the accompanying drawings, we realize that certain changes andmodifications therein may well occur to those skilled in the art withinthe broad teaching hereof; hence, it is our intention that the scope ofprotection provided hereby shall be limited only insofar as saidlimitations are expressly set forth in the appended claims.

What is claimed is:

1. A rifiescope which comprises, an elongate tubular barrel, objectivelens means mounted in the forward end of the barrel adapted to reproducean inverted and reversed image of a real object in a first image planelocated intermediate the ends of said barrel, a second tubular elementof smaller diameter than the barrel mounted therein for limiteduniversal tilting movement relative thereto, means adapted to receivethe image from the objective lens means and reproduce same in erectunreversed form at varying degrees of magnification in a second imageplane located a fixed distance behind the first image plane, said meanscomprising a pair of erector lens elements carried by the second tubularelement forwardly of the center of universal movement thereof thatcooperate to define an optical axis and are mounted for longitudinaladjustment relative to one another, ocular lens means located in therear extremity of the barrel and adapted to focus upon the erectunreversed image in the second image plane, first external adjustmentmeans carried by the barrel and operatively connected to the secondtubular element in longitudinally spaced relation to its center oflimited universal tilting movement, said adjustment means includingcontrol means adapted upon'actuation to tilt the second tubular elementand shift the optical axis defined by the erector lens elements so as tointroduce corrections for windage and elevation, second external meanslocated on the outside of the barrel connected to the erector lenselements and operable upon actuation to change the spacing therebetween,said second external means including a coupling extending into thebarrel and accommodating the tilting movement of the second tubularelement, a reticle carried by the second tubular element Within thesecond image plane which includes means defining an aiming point locatedon the optical axis defined by the erector lens elements, and adiaphragm car-- ried by the second tubular element for movementtherewith, said diaphragm having an aperture therein defining a field ofview which remains substantially unobstructed at maximum deflections ofthe second tubular element relative to the barrel.

2. The riflescope as set forth in claim 1 in which the second externalmeans comprises an elongate slot in the wall of the second tubularelement, a circumferential slot in the barrel opening onto the surfaceof the second tubulare element, a pair of tubular mounts for the erectorlens elements, each of said mounts being independently adjustablerelative to one another and longitudinally of the second tubularelement, a cam tube mounted exteriorly of the second tubular element forrotational movement relative thereto over the slot therein andunderneath the slot in the barrel, means carried by the cam tubeprojecting through the circumferential slot in the barrel for rotatingsaid cam tube relative to the second tubular element, said cam tubehaving a pair of cam slots therein intersecting the slot in the secondtubular element at longitudinally-spaced points varying in location andspacing depending upon the relative rotarial positions thereof, saidpoints of intersection defining the positions of the erector lenselements corresponding to a range of changes in degree of imagemagnification while maintaining said image focused in the second imageplane, and cam follower means operatively interconnecting each of theerector lens element mounts with one of the cam slots in the cam tube 12through the longitudinal slot in the second tubular element.

3. The riflescope as set forth in claim 2 in which, the means carried bythe cam tube projecting through the circumferential slot in the barrelcomprises a pin, an adjusting ring is mounted on the barrel for relativerotational movement, and the adjusting ring and pin are interconnectedsuch that rotation of said ring accomplishes the adjustment of theerector lens elements.

4. The riflescope as set forth in claim 3 in which the coupling of thesecond external adjustment means that accommodates the tiltable movementof the second tubu lar element comprises, a loose fit between theadjusting ring and barrel, a pairof longitudinally-spaced continuousannular grooves on the inside of the adjusting ring on opposite sides ofthe pin, and a pair of compressible elastic O-ring seals located withinthe annular grooves in contact with the barrel, said seals permittingsaid adjusting ring to tilt on the barrel the amount required toaccommodate the tilt of the second tubular element while sealing theinterior of the assembly against the entry of moisture-laden air.

5. The riflescope as set forth in claim 1 in which the diaphragm ispositioned closely adjacent the second image plane.

6. The rifiescope as set forth in claim 1 in which, the diaphragmcarries the reticle and both are located within the second image plane.

7. The riflescope as set forth in claim 1 in which, the diaphragmcarries the reticle and comprises a ring of lesser diameter than theinside of the second tubular element at the second image plane, thesecond tubular element includes abutment-forming means positioned andadapted to engage the diaphragm ring and locate same in the second imageplane when placed thereagainst, said ring being adjustable bothrotarially and eccentrically within said second image plane to place theaiming point of the reticle carried thereby on the optical axis of theerector elements, and means comprising a lock ring cooperating with thesecond tubular element to secure the diaphragm ring in adjusted positionagainst the abutment means.

8. The riflescope as set forth in claim 1 in which center of universalmovement of the second tubular element lies closely adjacent the secondimage plane.

References Cited by the Examiner UNITED STATES PATENTS DAVID H. RUBIN,Primary Examiner.

1. A RIFLESCOPE WHICH COMPRISES, AN ELONGATE TUBULAR BARREL, OBJECTIVELENS MEANS MOUNTED IN THE FORWARD END OF THE BARREL ADAPTED TO REPRODUCEAN INVERTED AN REVERSED IMAGE OF A REAL OBJECT IN A FIRST IMAGE PLANELOCATED INERMEDIATE THE ENDS OF SAID BARREL, A SECOND TUBULAR ELEMENT OFSMALLER DIAMETER THAN THE BARREL MOUNTED THEREIN FOR LIMITED UNIVERSALTILTING MOVEMENT RELATIVE THERETO, MEANS ADAPTED TO RECEIVE THE IMAGEFROM THE OBJECTIVE LENS MEANS AND REPRODUCE SAME IN ERECT UNREVERSEDFORM AT VARYING DEGREES OF MAGNIFICATION IN A SECOND IMAGE PLANE LOCATEDA FIXED DISTANCE BEHIND THE FIRST IMAGE PLANE, SAID MEANS COMPRISING APAIR OF ERECTOR LENS ELEMENTS CARRIED BY THE SECOND TUBULAR ELEMENTFORWARDLY OF THE CENTER OF UNIVERSAL MOVEMENT THEREOF THAT COOPERATE TODEFINE AN OPTICAL AXIS AND ARE MOUNTED FOR LONGITUDINAL ADJUSTMENTRELATIVE TO ONE ANOTHER, OCULAR LENS MEANS LOCATED IN THE REAR EXTREMITYOF THE BARREL AND ADAPTED TO FOCUS UPON THE ERECT UNREVERSED IMAGE INTHE SECOND IMAGE PLANE, FIRST EXTERNAL ADJUSTMENT MEANS CARRIED BY THEBARREL AND OPERATIVELY CONNECTED TO THE SECOND TUBULAR ELEMENT INLONGITUDINALLY SPACED RELATION TO ITS CENTER OF LIMITED UNIVERSALTILTING MOVEMENT, SAID ADJUSTMENT MEANS INCLUDING CONTROL MEANS ADAPTEDUPON ACTUATION TO TILT THE SECOND TUBULAR ELEMENT AND SHIFT THE OPTICALAXIS DEFINED BY THE ERECTOR LENS ELEMENTS SO AS TO INTRODUCE CORRECTIONSFOR WINDAGE AND ELEVATION, SECOND EXTERNAL MEANS LOCATED ON THE OUTSIDEOF THE BARREL CONNECTED TO THE ERECTOR LENS ELEMENTS AND OPERABLE UPONACTUATION TO CHANGE THE SPACING THEREBETWEEN, SAID SECOND EXTERNAL MEANSINCLUDING A COUPLING EXTENDING INTO THE BARREL AND ACCOMMODATING THETILTING MOVEMENT OF THE SECOND TUBULAR ELEMENT, A RETICLE CARRIED BY THESECOND TUBULAR ELEMENT WITHIN THE SECOND IMAGE PLANE WHICH INCLUDESMEANS DEFINING A AIMING POINT LOCATED ON THE OPTICAL AXIS DEFINED BY THEERECTOR LENS ELEMENTS, AND A DIAPHRAM CARRIED BY THE SECOND TUBULARELEMENT FOR MOVEMENT THEREWITH, SAID DIAPHRAGM HAVING AN APERTURETHEREIN DEFINING A FIELD OF VIEW WHICH REMAINS SUBSTANTIALLYUNOBSTRUCTED AT MAXIMUM DEFLECTIONS OF THE SECOND TUBULAR ELEMENTRELATIVE TO THE BARREL.